Conventionally, as an electric wire for automobile wiring, an electric wire having following properties has been mainly used: the electric wire which includes a stranded conductor obtained by stranding annealed copper wires according to JIS C 3102 or annealed copper wires subjected to tin plating or the like, as a conductor; and an insulator such as vinyl chloride or crosslinked polyethylene covering the conductor.
In recent years, the number of wiring positions increases with increase of the number of control circuits to be mounted on various electronic devices accompanying high performance and high function of automobiles. Accordingly, automobiles have became heavier due to the wirings while the wirings have been required for further reliability satisfying the high performance and high function of automobiles. In addition, reduction in diameter of the wire is required in response to the demand for reduction of the wiring in volume and making the automobile lightweight. Further, an electric wire for automobile is required to be readily reusable from the viewpoint of growing tendency of environmental protection. Meanwhile, the length of the wiring to a motor increases in an electric motorcar or a hybrid car in which a battery is mounted on the rear of the vehicle in terms of balance of the center of gravity or the like, Therefore, it is also required to decrease the weight of wiring materials.
For complying with these requirements, there is an electric conductor for automobiles in which desired electrical conductivity and solderability have been improved while bending resistance and tensile strength have been enhanced, by using a composite wire prepared by coating a steel wire with copper (e.g., JP-A-03-184210 (“JP-A” means unexamined published Japanese patent application)).
Further, there is a conductor of an electric wire for automobiles having a conductor sectional area of the upper limit of from 0.3 mm2 to 2.0 mm2 in which reduction of weight and possibility for reusing are improved and mechanical strength is ensured, by decreasing diameter of the conductor of an electric wire obtained by stranding hard drawn copper solid conductors and annealed copper solid conductors without using copper alloy wires (e.g., JP-A-06-060739).
Furthermore, there is a conductor of an electric cable for wiring for solving problems of electric connection by using a conductor for wiring formed by coating an aluminum wire with a zinc alloy, whereby copper is not mingled in reusing of automobiles since no copper materials are used, to suppress quality of steel materials to be reused from deteriorating (e.g., JP-A-06-203639).
In addition, there is a conductor composed of an aluminum alloy mainly used for aerial electric wires (e.g., JP-A-51-043307 and U.S. Pat. Nos. 3,697,260 and 3,773,501).
However, the above-described conductors of an electric wire for automobiles described in JP-A-03-184210 and JP-A-06-060739 are composed of a copper or a copper alloy. Therefore, they are still heavy weight. In addition, a solder is used for connecting the conductors. Accordingly, it has been a serious problem in reusing because lead or the like contained in the solder used at the time of connecting the conductor is one of environment pollutants.
The wire harness conductor for automobiles using an aluminum wire coated with a zinc alloy, as described in JP-A-06-203639, is quite effective as a part of attaining easy reusability and reduction of weight. However, the aluminum wire used for usual thin electric wires is mainly composed of hard drawn aluminum electric wire (JIS C 3108) and the like. Therefore, bending resistance of the wire is remarkably low as compared with a copper wire. Accordingly, if the aluminum electric wire is used at a place where repeated open and close action are occurred, such as a door hinge of the automobile, the aluminum electric wire is broken in earlier stage than the copper wire, and then it causes a problem that the aluminum wire cannot be used in conventional structural portions.
In the aluminum alloy electric wire described in JP-A-51-043307, bendability is only improved to an extent required for passing through a pulley in wiring works of the aerial power transmission wire. Thus, this wire does not satisfy bending resistance required in the aluminum conductor for automobiles that can be used in the present invention. In addition, since the diameter of the wire is large, it is hardly used as the aluminum conductor for automobiles that is prepared by stranding wires having a small diameter.
In U.S. Pat. No. 3,697,260, there are descriptions about flexibility, and breaking elongation is examined as a basis for evaluation of flexibility. However, this basis fundamentally differs from that in automobile technologies where a conductor having excellent bendability is required in terms of facilitating work efficiency for three-dimensional wiring of the electric wire in the body. Further, as bending resistance, evaluation is conducted by breaking after flexing several ten times. However, this basis for evaluation fundamentally differs from that for showing performance level required in the door of automobile, in which bending after flexing tens of thousands of times is necessary. Furthermore, the wire is a communication cable and, therefore, has a large diameter. Accordingly, it is difficult to apply the wire to the aluminum conductor for automobiles prepared by stranding wires having a small diameter.
While there are descriptions about bendability in U.S. Pat. No. 3,773,501, curvature of breaking by bending is evaluated using the wire's own diameter as a unit. However, this basis for evaluation also fundamentally differs from that for showing performance required in the door or the like of the automobile, in which bending after flexing tens of thousands of times is necessary. Further, since the wire is for use in aerial cables, the wire has a large diameter. Thus, the wire is hardly applicable to the aluminum conductor for automobiles that is prepared by stranding wires having a small diameter. Further, Sb is necessarily included.
Other and further features and advantages of the invention will appear more fully from the following description, appropriately referring to the accompanying drawings.